1. Field of the Invention
The present invention relates to a waveform equalizer in a recorded information reproduction device for reproducing recorded information from recording media.
2. Description of Related Art
Known is a technique of waveform equalization for improving the S/N ratio of a read signal read from a recording medium on which digital data is recorded at high densities, by performing filtering for strengthening high frequency enhancement on such a read signal. With this technique, the stronger the enhancement of high frequencies of the read signal, the more the S/N ratio can be improved. However, if the high frequencies are strengthened excessively, it will cause an increase in inter symbol interference. To cope with this problem, a waveform equalizer, that can perform high frequency enhancement without causing an increase in inter symbol interference is suggested in Japanese Patent Kokai No. H11-259985.
In such a waveform equalizer, however, a problem exists that a value at the zero-cross point of the read sample value sequence after equalization correction varies when the shortest run length of a read signal is short and thus inter symbol interference is increased, thereby high frequency regions cannot be sufficiently strengthened.